Spectrometer



V.May 12, 1942. yT. A. CUTTING 1 2,282,643

SPECTROMETER Filed OCT.. 25, 1940 Patented May 12, 1942 UNITED STATES PATENT OFFICE sPEc'raoME'rEa Theodore A. Cutting, Campbell, Calif.

Application October 25, 194A),v Serial No. 362,735

(C1. lis-14) 8 Claims.

My invention relates to improvementain spectroscopes and the object of my improvement is' to provide a compact, reflecting, diiraction grating spectrometer and spectrograph with a horizontal slit and a vertically arranged scale. Further objects are to provide adjusting means for the reecting grating, the eye lenses, and the arc, and to provide means for simultaneously viewing both spectrum and scale. Stillfurther objects are to provide means for converting the spectrometer into a spectrograph and to provide a new type of diiration grating, combining grating, reflector, and magnier. Still another object is to provide means for keeping the eye lenses in focus of the reflector and properly trained upon the diiraction grating as they move over the spectrum.

In the drawing:

Figure I is a plan view ofthe top removed,

Figure l1 is a side view with casing removed,

spectrometer,

Figure III is an end view ofthe spectrometer,`

and l Figure IV a side view of the reecting grating. The spectrometer is provided with a reecting dow I8 and directs a beam of light from the arc upon grating I.

. This beam of light may be reected up or down by rotating the mirrored grating I between the supporting standards 3, and may be reflected to left or right by moving turntable 2 about screw 1. After reflection from the grating, part of this beam of light becomes the spectrum of diffraction grating I, mounted upon a circular turntable 2 and pivotally held between standards 3 rising from turntable 2. The turntable, held by screw 1, is mounted upon the base 4 of the spectrometer.

' The whole instrument may be enclosed by walls 5 and cover 6, with the exception of the. l

square space in the corner occupied by the electric arc, the carbons 8 of which are arranged horizontally and secured by holders 9. The ore to be analyzed is placed upon a strip of metal whose lower portion I0 slides in track II, and whose upper part I2 is bent at right angles to serve as a table upon which to burn the ore I3. Instead of packing the powdered rock into a hollow carbon, as is customary, a fragment is placed upon the table I2, which is then pushed up until the substance to be analyzed is directly beneath.

or in the arc.

lCover B does not extend over the arc, but is cut away at the corner to keep the arc open and cool. The arc is mounted upon a block I4, sliding between two guides I5 so that it may easily be aligned with slit 2| and grating I. Light from the arc enters the casing through window It in wall II, and a strip of glass I9, painted black, slides vertically in track 20 over window I8. A,ne line scratched in the paint may constitute the spectroscopic slit 2|. The strip is pushed down until the slit 2| registers with winthe substance being burned in the arc, and the grating is turned so as to bring the spectrum directly `alongside the scale 23.

Scale 23, attached to wall I6, and curved in an arc, is calibrated directly in Angstrom-units so that the observer may instantly read the wave length of any spectral line by looking through the eye lens 21 and noting both spectrum and scale simultaneously. The eye lens 21 and the eld lens 28 are mounted upon a rod 29, sliding at oneend in a hole 38 in standard 3B, and bolted at the other end to rod 24. Scale 23 is magnified by the eye lens 21 and lies between lenses 21 and 28. When the free end of rod 29 28 is not absolutely essential to the instrument,

and may be made slidable upon rod 29 for focusing, or may even be dispensed with.

It has been found that an eye lens, to produce clearly focused lines at all points of the spectrum produced by the combination reflecting and magnifying grating must move in an arc of a circle having a radius equal to about one half of the distance between slit and grating. Rod

24, therefore, is given this length and anchored at one end to the block 31, midway between slit 'and grating. Rod 29 is bolted to rod 24 by a ried by it are made to swing in the. desired arc. Since the opposite end of rod 29 slides in a hole 38 in standard 30, near the grating, the lensesV are kept in constant alignment with the grat'-A ing I.

For converting the spectrometer into a spec-:,. trograph a photographic film is attached to the??- rear of scale 23, rod 29 is lowered or removed, and end wall 32 applied to exclude au light from ment of the eye lens 21, and hence the scale 23 is always in focus when once properly adjusted.

By tightening thumb nuts 25 and 26 sufficient joint friction is caused to keep arm 29 at any desired position without preventing its freedom of movement. Bolt holes 22 and 3i permit adjustments for securing proper distances between` lenses and grating.

The reflector I is a combination unit consisting of a plano-convex lens 36, a diffraction grating 33 upon its plane side, a reflecting medium 3l backing the grating, and a protective coating 35 of paint or shellac at the back. The diffraction grating 33 may consist of actual rulings upon the plane surface of the lens 36 or of a replica grating attached to the plane surface. The reflecting surface 34 may be a coating of silver, aluminum, or other reflecting-material. Of course the conventional concave diffraction grating may also be used` in this spectrometer with no other change than its substitution for the unit herein described. i

Light rays striking the reflector unit I, passing through to the reflector and back again will be twice refracted as by a double convex lens and will yield a magnified image similar to that of a. concave mirror. The focal length of the unit will depend upon the convexity of the lens. The'unit will consequently yield a magnified spectrum similar to that produced by a concave reflecting diffraction grating.

I claim:

LA spectrometer having a casing, a slit at one end of said casing, a reflecting diffraction grating at the other end of said casing, a standard near said grating, a holein said standard, a rod with one end slidably engaged in said hole and loosely enough held to permit also vertical pivotal movement and with a free end near said slit, an eye lens mounted upon the free end of said rod for viewing the spectrum produced by said grating, a eld lens between said eye lens eye lens mounted upon the free endoi said rod for viewing the spectrum produced by said grating, an arm pivotally attached to the base of said casing approximately midway between said slit and said grating and pivotally attached with the spectrum occupying the remainder of Cil and said grating also mounted upon said rod, a

block attached to the base ofsaid casing midway between said slit and said grating, an arm pivotally bolted at one end to said block to permit vertical movement and pivotally bolted at the other e'nd to. the free end of said rod to cause said eye lens to move in an arc, and an arcuate scale concentric with the arc of movement lof said eye'lens and in the focus 'of said eye lens butoccupying only a portion of the field of the eye lens, the spectrum occupying the remainder of the field, the scale calibrated and positioned to indicate what portion of the spectrum is visible through the lens.

2. A spectrometer having a casing, a. window in the end wall of said casing, a slide covering said window, a slit in said slide to admit a flattened beam of light to said casing, a plano convex lens at the opposite end of said casing receiving light from said slit, a diffraction grating attached to the plane side of said lens, a mirrored surface backing said grating, a standard near said grating, a rod slidably and pivotally attached to 'said standard at the level of said grating and with its free end pear said slit, an

the field, the scale calibrated and positioned to indicate the portion of the spectrum visible through the lens.

3. The combination of a base, an arc with horizontally arranged carbons mounted upon a corner of said base, a reflecting diffraction grating mounted upon the opposite end of said base,

a wall between said arc and said grating, a horizontal slit in said wall for passing light from said arcto said grating, an eye lens at one side of said arc, a partition between said are and said eyelens, a rod with one end slidably and pivotally supported at the level of said grating and the other end supporting said eye lens and training it upon said grating, and an arm pivotally attached at one end to the base approximately midway between said slit and said grating and pivoted at the other end to said lens rod to impart to its free end an arcuate movement for keeping the spectrum in focus as the eye lens moves up and down in the path of the spectrum.

4. A spectrometer having a base, a wall rising from said base, a slit in said wall; a magnifying, recflecting, diffraction grating receiving light from said slit; an eye lens in the path of the spectrum reflected from said grating, a rod slidingly and pivotally engaged at one end near said grating and supporting at the free end said eye lens; an arm pivoted at one end to said base, approximately midway between said slit and said grating, so as to permit vertical rotation, and pivotally bolted at the other end to said rod near the eye .lens, thereby causing said eye lens to move in an arc; bolts at both ends of 'said arm to permit vertical pivotal movement, a wavelength scale concentric with the path of movement of said eye lens and in the focus of said eye lens, extra bolt holes in said rod and said arm to permit focal adjustments, and wing nuts upon the bolts holding said arm and said rod for the regulation of frictionso that the eye lens may be moved up or down, but yet remain fixed at any desired position.

5. A combination spectrometer and vspectrograph having a casing, a horizontal slit in said casing, a diffraction grating with horizontal rulings receiving the beam of light from said slit, a lens for magnifying the spectrum produced by said grating, an eye lens at the focus ofy said magnifying lens for viewing the spectrum, means for'moving said eye lens for viewin-g different parts of the spectrum, supporting means concentric with the path of movement of said eye lens and between part of said eye lens and said grating, for holding on one side a scale and upon the other a photographic lm, -and means 4for excluding from the casing all light except that entering the slit.

6. A spectroscope having a base, a wall rising from said base, a slit in said wall, a plano-convex lens receiving the beam of light from said slit, a diffraction grating upon the plane side of said lens, a mirrored surface backing said grating, an upright attached to said base near said grating, aA rod slidably and pivotallyengaged at one end by said upright at a. point on a level with said grating and free at the other end for vertical movement, an eye lens at the free end of said rod, a block attached to said base approximately midway between said eye lens and said grating, an arm pivotally attached at one end to said rod near said eye lens and at the other to said block and causing the end of said rod with its lens to move in an arc, and a plurality of perforations in said block for adjustment of the arm attached thereto.

7. A spectroscope having a base, a wall at one end of said base; a slit in said wall, a reflecting light dispersing means at the other end of said base receiving light from saidslit, a member with one end slidably and pivotally supported near said dispersing means, an ocular mounted at the opposite end of said member receiving the spectrum ren-acted from said light dispersing means,`

other end to said member near said ocular for imparting an arcuate movement to said ocular.

8. A combination spectrometer and spectrograph having a casing, a slit at one end of said casing, a reflecting light dispersing means at the opposite end oi said casing receiving light from said slit, an ocular to one side of said slit receiving the spectrum reected from said dispersing means, means for moving said ocular to different portions of the spectrum, supporting means concentric with the path of movement of said ocular and between part of said ocular and said dispersing means for holding on 'one side a scale and upon the other a spectrographic lm.

THEODORE A. CUTTING. 

